The present invention relates to power supplies, and more particularly, to power supplies for industrial and other harsh environments.
Industrial control applications, such as process control applications, often involve the use of distributed controllers, transducers and other devices. Many of these devices use low voltage DC power, e.g., 24 VDC power. Accordingly, in process control applications, such as those in a refinery or petrochemical plant, AC-powered, DC-output power supplies are often located near control equipment to provide low voltage DC power.
Many conventional process control systems use off-the-shelf DC power supplies. Although these supplies may be xe2x80x9cruggedizedxe2x80x9d to withstand high temperature and vibration levels, they may use open-frame designs with fan-forced cooling. Such open-frame designs may be vulnerable to damage in corrosive environments, and may be unacceptable for use in explosive environments. In addition, fan-cooled units may be vulnerable to fan failure or clogging due to accumulation of dust or other contaminants. Conventional power supply units may also exhibit less than desirable efficiency, which can, in turn, yield to more thermal stress and reduced reliability.
According to embodiments of the invention, an industrial power supply module includes a heatsinking structure, e.g., an extruded aluminum structure, including a plurality of walls joined to define a channel. A first circuit board assembly includes a booster circuit operative to receive an input voltage at an input port thereof and to produce a first DC voltage therefrom, and is mounted to the heatsinking structure such that at least a portion of the first circuit board assembly lies in the channel. A second circuit board assembly includes a DC/DC converter circuit electrically coupled to the booster circuit and operative to produce a second DC voltage at an output thereof from the first DC voltage produced by the booster circuit, and is mounted to the heatsinking structure such that at least a portion of the second circuit board assembly lies in the channel. First and second end caps are attached to the heatsinking structure at respective first and second ends of the channel, the first and second end caps and the walls of the heatsinking structure enclosing a volume including at least portions of the first and second circuit board assemblies therein.
The first circuit board assembly may be mounted to the heatsinking structure such that a surface of the first circuit board assembly conforms to the plurality of walls of the heatsinking structure at the first end of the channel to define a second enclosed volume within the first enclosed volume. The second circuit board assembly may be contained within the second enclosed volume. A first gasket may provide an environmental seal between the first circuit board assembly and the heatsinking structure at the first end of the channel, and a second gasket may provide an environmental seal between the second end cap and the heatsinking structure at the second end of the channel. In this manner, the second enclosed volume may be environmentally sealed. The module may further include a third circuit board assembly attached to the heatsinking structure outside of the sealed second enclosed volume. The third circuit board assembly may include a plurality of terminals that are electrically coupled to a portion of the first circuit board assembly extending outside of the sealed second enclosed volume.
According to other aspects of the invention, at least one of the first and second circuit board assemblies includes at least one electronic component disposed near a periphery of a corresponding at least one of the first and second circuit boards. The power supply module further includes a thermally conductive region that provides heat transfer between the at least one electronic component and an adjacent wall of the heatsinking structure. For example, the at least one heat-generating component may be a power transistor, and the thermally conductive region may be a ceramic insulator disposed between the power transistor and the adjacent wall of the heatsinking structure. The adjacent wall of the heatsinking structure may have a groove defined therein, and the power supply module may further include a retaining clip that engages the groove and compresses the transistor and the ceramic insulator against the adjacent wall of the heatsinking structure.
According to yet other aspects of the invention, an industrial power supply module includes a booster circuit operative to produce a first DC voltage at an output port thereof from either of an AC input voltage or a DC input voltage at an input port thereof. The module further includes a DC/DC converter circuit electrically coupled to the booster circuit and operative to produce a second DC voltage at an output port thereof from the first DC voltage such that the second DC is at least about ten times less than the first DC voltage. An enclosure encloses portions of the booster circuit and the DC/DC converter circuit within an environmentally sealed volume. The enclosure is thermally coupled to the booster circuit and the DC/DC converter circuit to provide heat transfer between the booster and DC/DC converter circuits and an external environment. The input port of the booster circuit and the output port of the DC/DC converter circuit are electrically accessible from outside of the sealed volume. The booster circuit may be operative to correct power factor at the input port.